This application claims the priority of German application 200 09 896.9, filed Jun. 2, 2000, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a mast for a carrying system having carriers which can be vertically moved by way of a runner guided on the mast and used for holding stage-related implements. The mast is constructed of several tube sections of the same diameter which are aligned with respect to one another and connected with one another at boundaries by an interior tube piece.
A carrying system of this type is known from German Patent Document DE 9217865 U1. In this system, masts which are erected in floor parts are provided. An erection hinge is provided between the floor part and each mast. For easier erection, this erection hinge connects the mast in a tiltable manner with a tube piece of the floor part.
Since such carrying systems have to be moved to just below the ceilings of rooms, for example, for television or film shots, the masts are, as a rule, constructed of several sections in order to simplify transport of the carrying system to and from the erection site.
In carrying systems intended for large loads such as, for example, a number of flood lights or the like, correspondingly stable mast sections which are to be held on one another without play have to be used in order to ensure stability. So far, this has not been achieved in a sufficiently secure manner.
It is therefore an object of the present invention to construct a carrying system of the initially mentioned type such that the masts, which are constructed of sections, can be assembled in an extremely stable manner.
For achieving this object, in a mast for a carrying system of the initially mentioned type, the interior tube piece consists of a sleeve which is slotted along a surface line and penetrated by a pressure screw, which acts by way of a pressure piece with a convex outer contour, onto counterpressure pieces which are provided on the edge of the slot and also have convex outer contours.
In an extremely simple manner, this permits the successive conversion of the pressure forces introduced along a radial plane through the center of the interior tube piece to forces which lead to a spreading-open of the sleeve along its entire diameter and which do not only cause locking in the area of the slot. This invention, therefore, causes a close, tight and play-free fit of the interior tube piece on the mast sections in the area of their boundaries. As a result, a mast constructed in this manner can be made as stable as a continuous one-piece mast.
As a further development of the invention, the pressure screw can be situated in a radial plane extending through the slot and, in this manner, can cause the desired distribution of the spreading forces. Naturally, several pressure screws, and preferably two, can be provided along the length of the interior tube piece, with each of these screws extending at the same axial distance from the boundary of the mutually joined mast sections.
As a further development of the invention, each of the outer contours of pressure pieces and counterpressure pieces can be a circular-cylindrical surface. This permits the use of prefabricated profile parts. In this case, a pressure piece can be applied to a pressure screw which is provided with a nut resting against a guide piece, with the pressure piece being provided on the guide piece.
As still a further development of the invention, an axial stop can be provided on the side situated opposite the pressure piece. This axial stop, in turn, rests on a rectangular profile resting against the tube wall. This further development prevents a co-rotation of the thread guide when the pressure screw is adjusted.
As yet a further development of the invention, the interior tube piece can be provided with openings for guiding a turning tool for the pressure screw through. The interior tube can also be provided with at least one radial pin which, in particular, projects from the transverse center plane and, as an axial stop, engages in a recess at the boundary between the adjacent mast sections when the mast sections are assembled. This further development ensures correct arrangement of the interior tube piece in the longitudinal direction of the mast sections and simultaneously ensures that the openings for guiding through a turning tool arrive in a position in which they are aligned with corresponding openings in the mast sections.
Finally, it is also possible to provide an extension sleeve at the application head for operating the pressure screw. The extension sleeve reaches through the openings provided in the mast sections and therefore contributes to axially securing the mast sections with respect to one another. This may be particularly necessary when, in addition to the pressure forces upon the mast sections which are normally expected, tension forces may also occur. This can happen, for example, when the masts are not only used for guiding carriers in interior spaces but for the arrangement of a roof in the open air. Wind forces, which act upon the roof, can result in tension forces in the masts. However, if such a carrying frame is provided, then the extension sleeve should not extend to the outside beyond the outer contour of the mast sections in order to ensure perfect free guiding of the runner for the carrying frame.
An embodiment of the invention is illustrated in the drawing figures and is explained in the following description.